Topics:

...aggression

The link between gonadal steroids and aggression is often attributed to work conducted by Arnold Berthold in 1849.  It is commonly believed that high levels of the male gonadal steroid, testosterone, cause increased aggression.  However, this is not necessarily true in all contexts.  For example, species of hamster are actually less aggressive in the summer when they have their breeding season and high levels of gonadal steroid.